Residents of the Big Island were warned to take shelter from the ash as toxic gas levels spiked in a small southeast area where lava has burst from the ground during the two-week eruption, authorities said.

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The wind could carry Kilaueaâs ash plume as far as Hilo, the Big Islandâs largest city and a major tourism centre, the County of Hawaii Civil Defense warned in an alert.

âProtect yourself from ash fallout,â it said.

Geologists said the 4:15 a.m. (10:15 a.m. EDT) explosion was likely the first in a series of steam-driven blasts last seen in 1924, rather than âthe big oneâ that nervous residents had feared as Kilauea was rocked by earthquakes in recent days.

A spike in toxic sulphur dioxide gas closed schools around the village of Pahoa, 25 miles (40 km) east of the volcano, where lava from fissures has destroyed 37 homes and other structures and forced about 2,000 residents to evacuate. National guard troops were forced to don gas masks at a nearby road intersection, according to a Reuters reporter.

Civil defence worker s handed out one ash mask per family member in communities close to Kilauea, such as the village of Volcano, which was expected to receive a 1/32 of an inch (0.8 millimetres) dusting of ash, according to USGS estimates.

USGS geologists and staff were evacuated from the Kilauea summit shortly before the explosion.

âTall but smallâ

Thursdayâs eruption lasted only a few minutes, said Coombs who called it âa big event that got peopleâs attention, but did not have widespread impact.â

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âTall but small,â she said of Thursdayâs plume.

An aviation red alert was in effect due to risks ash could be carried into aircraft routes and damage jet engines, USGS said. Passenger jets generally cruise at around 30,000 feet, the height of Thursdayâs plume.

Pahoa fire station on Thursday morning recorded a âred levelâ of sulphur dioxide, m eaning it would cause choking and an inability to breathe, Fenix Grange of the Hawaii Department of Health told a news conference in Hilo. âIf itâs red, itâs get out of Dodge,â She said. âWeâre trying to create a ring around sulphur dioxide so we can protect people.â

Avoid driving

Across the Big Island, home to 200,000 residents, people were encouraged to avoid driving in ashfall areas, as the powdered rock makes roads slippery, and not go outdoors unless necessary.

Geologists had warned that a chain of explosive eruptions could begin once Kilaueaâs falling lava lake descended below the water table, allowing water to run on to the top of the lava column and create steam-driven blasts.

âI donât think there is a big one thatâs coming,â said University of Hawaii volcanologist Scott Rowland. âI think itâs going to be a series of explosions similar to the one that happened this morning, and thatâs based on what happened in 1924, which is really our only analogue.â

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In the 1924 eruption, which lasted 2-1/2 weeks, one person was killed by debris shot from the crater and areas as far as 35 miles (56 km) to the southwest and 30 miles (48 km) to the east were dusted with ash, according to the USGS.

There have been no deaths or serious injuries reported during the current eruption.

Hawaii's Kilauea volcano starts spewing large chunks of rock. Geologists say these 'ballistic blocks' could be the precursor to a major violent eruption. Source: Google News